Possible NULL pointer deferenced (src/interfaces/libpq/fe-exec.c (line 563)

Hi Mark,
please, can you take a look?

This possible bug was appeared before, see at:
1. https://bugzilla.redhat.com/show_bug.cgi?id=879803

The trap still persist, in HEAD see:

src/interfaces/libpq/fe-exec.c (line 563)
/* If there's enough space in the current block, no problem. */
if (nBytes <= (size_t) res->spaceLeft)
{
space = res->curBlock->space + res->curOffset;
res->curOffset += nBytes;
res->spaceLeft -= nBytes;

return space;
}

The res->curBlock pointer possibly, can be NULL here (line 563).

See at:
src/interfaces/libpq/fe-exec.c (line 585)
if (res->curBlock)

The path is res->curBlock be NULL and res->spaceLeft > nBytes.

If res->curBlock it not can be NULL, inside pqResultAlloc function, why is
verified against NULL at line 585?

regards,
Ranier Vilela